A lighting system that includes a plurality of light sources may locate circuitry common to all of the light sources, such as a power supply, in a central controller rather than including redundant copies of the circuitry at each light source. A central power supply, for example, may reduce the cost of the lighting system, due to the fewer total components used, as well as reduce the power consumed by the system, allow for smaller and cooler light sources, and provide a more convenient point of access for maintenance or repair. Such a system may distribute a power bus from the central controller to the plurality of light sources, which may be widely distributed across a room, building, or other area.
In addition to distributing power, the central controller may change the brightness, color, or other such property of one or more of the light sources from a single, easily accessible location. Status information, such as temperature, may be sent from the light sources to the central controller, which may automatically adjust a property of the light sources in response to the information or may present the information to a user. The commands to the lights and the information read from the lights, may be sent and received using one or more buses routed, in addition to the power bus, between the central controller and the light sources. More buses may, however, mean more cost added to the system and more difficulty in installing and maintaining the system.
In some systems, the power bus is also used as a command bus by piggybacking a high-frequency communication signal on top of the low-frequency power signal. These systems are, however, susceptible to noise and/or transmission issues, causing commands sent to the lighting units to be misinterpreted or missed and data received from the lighting units to be corrupted. Furthermore, identifying one lighting unit amongst the plurality of units connected to the central controller may be difficult or impossible, preventing individual control of a single lighting unit. This difficulty is compounded in systems where the number of lighting units is not known at the time of manufacture or installation (e.g., lighting units may be added or removed from the system during its installed lifetime) because the central controller may not be able to identify the addition or removal, causing further communication problems.
A need therefore exists for a lighting system featuring a central controller capable of communicating reliably and dynamically with any number of lighting units over a single, combined power and command bus.